This invention relates generally to electrical apparatus, and more particularly to a gas-insulated bushing which utilizes sliding contact fingers to maintain electrical contact in an expansion joint.
Gas-insulated electrical bushings are generally utilized for providing connections between overhead electric power transmission lines and elements of gas-insulated substations. These bushings typically comprise a hollow, elongated outer insulating shell, a centrally disposed electrical conductor disposed within the shell, and an insulating gas electrically insulating the electrical conductor from the insulating shell. The electrical conductor is used to transfer power from the transmission line to the associated substation equipment. In so transferring this power, though, the electrical conductor itself is heated, and this heating results in thermal expansion and contraction of the electrical conductor. This thermal expansion and contraction must be compensated for in the design of the bushing so as to maintain both a positive pressure seal within the insulating shell, and positive electrical contact between the conductor and the terminal connected to the power line. Prior art bushings utilized an expansion cap which included a diaphragm in the form of a thin metal spinning to provide for expansion and contraction of the bushing conductor due to the thermal stresses imposed upon it. However, use of this diaphragm has certain drawbacks, the most serious of which involves the difficulty of welding to this diaphragm.